This invention relates to guide wires for use in small bore blood vessels such as those involved in cardiovascular surgical procedures. More particularly, the invention concerns a guide which can be steered into and along very narrow blood vessels (including naturally narrow vessels as well as stenosed vessels) to locate its distal end in a precise position. Once so placed, a catheter can be advanced over the guide wire directly to the particular site in the patient's cardiovascular system. The invention is of particular importance in coronary dilatation techniques where the catheter is itself very small in diameter and is difficult to advance and place deeply in the patient's cardiovascular system, as is the case when trying to reach a coronary artery.
Before the present invention there was no satisfactory guide wire for use with such small diameter catheters. Typically the procedure for advancing a dilatation catheter into the coronary artery has been to use a relatively stiff, large diameter, conventional coronary angiographic catheter as a guide through which the smaller diameter dilatation catheter is advanced. In that technique the relatively large diameter guide catheter is advanced and manipulated to locate its distal end at the entry to the coronary artery. The more slender, flexible dilatation catheter then is passed through the guide catheter so that the distal end of the dilatation catheter will exit from the guide catheter and, hopefully, will enter the entrance to the coronary artery. The technique, which is disclosed in U.S. Pat. No. 4,195,637 to Gruntzig, requires that the dilatation catheter be pushed through the guide catheter and then into and through the coronary artery. Typically it is required to push the dilatation catheter so that its balloon passes through or into the mass of stenotic material which obstructs the coronary artery. Because of the slender, flexible and delicate nature of the coronary dilatation catheter such advancement and placement of the dilatation catheter is a delicate, difficult procedure calling for a great deal of skill, care and patience.
While suggestions have been made to use a guide wire to advance such a slender catheter as a coronary dilatation catheter, no suitable device was known which could serve properly as a guide wire while being small enough to permit the relatively small diameter dilatation catheter to be slipped over and advanced along the guide wire. Because the guide wire of the type of which the present invention is concerned is much smaller than a conventional guide wire (of the order of 0.018" diameter as compared to a conventional guide wire approximately 0.038" diameter), numerous additional difficulties in the construction and use of such a guide wire are presented. For example, using a smaller guide wire typically tends to result in reduced stiffness and, therefore, is more difficult to control and manipulate. A smaller diameter guide wire typically may be expected to be more fragile and more susceptible to breakage. Less torque can be transmitted along a smaller diameter, more delicate guide wire, particularly a guide wire which utilizes conventional construction in which substantially the full length of the guide wire is in the form of a helically wound spring wire. Additionally, a smaller guide wire is more difficult to observe fluoroscopically. That problem is pronounced particularly with heavier patients whose additional tissue makes it more difficult to observe fluoroscopically the position of the guide wire. It may be possible to observe fluoroscopically the position of a smaller guide wire in such a patient.
It is among the general objects of the invention to provide a guide wire construction which is of very small diameter, suitable for use with catheters intended to be advanced into small bore arteries such as, for example, a coronary dilatation balloon catheter, which avoids the foregoing, and other difficulties.
In accordance with the present invention the guide wire includes a main rod or wire of a small diameter which extends substantially the full length of the guide wire. The main wire is of uniform diameter except for the distal portion which is provided with a progressively narrowing taper. The tapered distal portion of the main wire is surrounded by a helically coiled spring. In the preferred embodiment the proximal end of the spring is secured to the main wire where the wire begins to taper and the distal end of the spring is secured to the distal end of the main wire, where the taper is most narrow. The distal end of the helical spring extends slightly beyond the distal tip of the main wire, for approximately one centimeter to define a spring extension. The spring extension tip is highly flexible and delicate and may bend and flex easily. It serves as a soft, flexible, resilient bumper for the distal tip of the guide wire, thereby minimizing the chance of trauma or injury to the blood vessel. The main spring and the distal bumper spring are formed from a material having a high radiopacity. Although not essential, the main wire also may be formed from a material having a high degree of radiopacity.
A high degree of torque control is provided by the rotationally rigid wire which makes up the major portion of the length of the guide wire. The use of a rotationally rigid wire over the major length of the guide wire assures that most of the torque applied at the proximal end will be transmitted fully to the distal region, unlike more conventional guide wires in which the torque tends to twist and distort the guide wire.
The distal region of the guide wire which includes the tapered safety wire and surrounding spring may be bent manually by the surgeon to a predetermined curve so that the distal portion of the guide will be biased toward that curved shape. The curve enables the guide to be advanced selectively into various branches at blood vessel bifurcates by controlling the rotation of the wire from its proximal end. The progressive taper at the distal region of the wire provides for a distal region with a main spring which increases in flexibility as it approaches the distal tip. Risk of trauma to the blood vessel is minimized by the highly flexible short bumper spring extension at the distal tip of the device.
Another aspect of the invention relates to the configuration of the dilatation catheter in combination with the small diameter guide wire. The catheter is constructed so as to have a main lumen which is dimensioned and shaped with respect to the guide wire so that even when the guide wire is in place within the main lumen there still is adequate cross-sectional flow area in the lumen. Thus the guide wire need not be removed in order to administer fluids to the patient or to take pressure measurements or the like.
It is among the objects of the invention to provide a small diameter guide wire which provides a high degree of steerable control and which may be placed with precision so as to serve as a guide for a catheter.
Another object of the invention is to provide a small diameter guide wire of the type described in which the distal portion may be pre-bent into a predetermined curve to facilitate steering of the wire by rotational control from the proximal end of the guide wire.
A further object of the invention is to provide a small diameter guide wire in which the distal portion is of increasing flexibility.
Another object of the invention is to provide a small diameter guide wire which has reduced risk of trauma to the inner surface of small bore blood vessels.
A further object of the invention is to provide small diameter guide wire having increased fluoroscopic visibility.
Another object of the invention is to provide a small diameter guide wire suitable particularly for use with balloon dilatation coronary catheters.
Still another object of the invention is to provide an improved combination of balloon dilatation catheter and guiding means therefor to advance the balloon dilatation catheter.
A further object of the invention is to provide a guide wire for use with a balloon dilatation catheter which facilitates the speed with which a vascular or coronary dilatation procedure can be performed.
Still another object of the invention is to provide a combination dilatation catheter and guide wire therefor in which the guide wire need not be removed in order to deliver fluids through the catheter or to make pressure measurements.